Image projection apparatus and control method thereof

ABSTRACT

An image projection apparatus comprises a projection unit configured to project an image onto a projection plane, a correction unit configured to correct a range of the image projected by the projection unit, a deformation unit configured to deform the projected range of the image according to a designated correction point, and a control unit configured to optically change the projected range of the image projected by the projection unit according to a designation of an outside of a predetermined range as the correction point.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image projection apparatus andcontrol method thereof.

2. Description of the Related Art

Conventionally, as a distortion correction method of an image projectionapparatus, a technique for attaining distortion correction by deforminga projected image according to move instructions of points of fourcorners from the user is known. However, with this technique, since thepoints of the four corners cannot be moved outside the projected image,the user has to set the image projection apparatus before distortioncorrection so that the projected image includes a screen.

For example, Japanese Patent No. 4578341 and Japanese Patent Laid-OpenNo. 2006-121240 disclose the following technique. Initially, beforedistortion correction, a shooting is performed in a projecting directionby an image capturing unit to recognize a positional relationshipbetween a projected region and projected image. Next, a zoom conditionthat the outer circumference of the projected image is not locatedwithin a screen region and the projected image becomes as small aspossible is calculated, a zoom lens is driven to satisfy that condition,and the image is then deformed to attain distortion correction of theprojected image.

However, the technique described in Japanese Patent No. 4578341 andJapanese Patent Laid-Open No. 2006-121240 requires the image capturingunit to recognize the projected region before distortion correction,resulting in an increase in cost. Also, when a projected region cannotbe specified from a captured image (for example, when an image isprojected onto a plain wall), distortion correction cannot beappropriately attained.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of theaforementioned problems, and realizes an image projection apparatus andcontrol method thereof, which can attain distortion correction of aprojected image to an appropriate size and shape without using anyimaging unit and independently of a positional relationship between theprojected image and projected region before distortion correction.

In order to solve the aforementioned problems, the present inventionprovides an image projection apparatus comprising: a projection unitconfigured to project an image onto a projection plane; a correctionunit configured to correct a range of the image projected by theprojection unit; a deformation unit configured to deform the projectedrange of the image according to a designated correction point; and acontrol unit configured to optically change the projected range of theimage projected by the projection unit according to a designation of anoutside of a predetermined range as the correction point.

In order to solve the aforementioned problems, the present inventionprovides a control method of an image projection apparatus having aprojection unit configured to project an image onto a projection plane,a correction unit configured to: correct a range of the image projectedby the projection unit, and a deformation unit configured to deform theprojected range of the image according to a designated correction point,the method comprising optically changing the projected range of theimage projected by the projection unit according to a designation of anoutside of a predetermined range as the correction point.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an image projectionapparatus according to an embodiment of the present invention;

FIG. 2 is a flowchart showing a basic operation of a projector accordingto the embodiment;

FIG. 3 is a block diagram showing an internal configuration of an imageprocessing unit according to the first embodiment;

FIG. 4 is a flowchart showing deformation processing according to thefirst embodiment;

FIGS. 5A and 5B are views for explaining deformation processing bycomparing a projected region on a liquid-crystal panel and thatprojected on a screen according to the first embodiment;

FIGS. 6A to 6F are views for explaining deformation processing accordingto the first embodiment;

FIG. 7 is a flowchart showing deformation processing according to thesecond embodiment;

FIG. 8 is a view for explaining projective conversion;

FIG. 9 is a flowchart showing a modification of step S406 in FIG. 4; and

FIGS. 10A to 10G are views for explaining deformation processingaccording to the second embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described in detail below.The following embodiments are merely examples for practicing the presentinvention. The embodiments should be properly modified or changeddepending on various conditions and the structure of an apparatus towhich the present invention is applied. The present invention should notbe limited to the following embodiments. Also, parts of the embodimentsto be described later may be properly combined.

First Embodiment

The following is a description of an embodiment in which an imageprojection apparatus according to the present invention is applied to,for example, a liquid-crystal projector that projects image.

<Apparatus Configuration>

A configuration and functionality of the image projection apparatus ofthe embodiments of the present invention will now be described withreference to FIG. 1.

A liquid-crystal projector (to be simply referred to as a projectorhereinafter) of this embodiment controls light transmittances ofliquid-crystal elements in accordance with an image to be displayed toproject light which comes from a light source and is transmitted throughthe liquid-crystal elements onto a screen, thereby projecting the imageto the user. FIG. 1 shows the overall arrangement of a projector 100 ofthis embodiment.

The projector 100 of this embodiment includes a CPU 110, ROM 111, RAM112, operation member 113, image input unit 130, and image processingunit 140. Also, the projector 100 includes a liquid-crystal control unit150, liquid-crystal elements 151R, 151G, and 151B, light source controlunit 160, light source 161, color separating unit 162, color composingunit 163, optical system control unit 170, and projection optical system171. Furthermore, the projector 100 may also include arecording/reproduction unit 191, recording medium 192, communicationunit 193, imaging unit 194, display control unit 195, and display unit196.

The CPU 110 controls respective operation blocks of the projector 100.The ROM 111 stores a control program which describes the processingsequence of the CPU 110. The RAM 112 temporarily stores the controlprogram and data as a work memory. The CPU 110 temporarily stores stillimage data or moving image data reproduced from the recording medium 192by the recording/reproduction unit 191, and can reproduce the image orvideo using the program stored in the ROM 111. Also, the CPU 110temporarily stores still image data or moving image data received by thecommunication unit 193, and can reproduce the image or video using theprogram stored in the ROM 111. Furthermore, the CPU 110 temporarilystores an image or video obtained by the imaging unit 194 on the RAM112, converts the stored image or video into still image data or movingimage data using the program stored in the ROM 111, and can record theconverted data in the recording medium 192.

The operation member 113 includes, for example, switches, dials, a touchpanel arranged on the display unit 196, and the like, accepts a userinstruction, and transmits an instruction signal to the CPU 110. Also,the operation member 113 may transmit a predetermined instruction signalto the CPU 110 based on a signal received by, for example, a signalreceiving unit (for example, an infrared receiving unit) which receivesa signal from a remote controller (not shown). The CPU 110 receives acontrol signal input from the operation member 113 or communication unit193, and controls the respective operation blocks of the projector 100.

The image input unit 130 receives an image signal or video signal froman external apparatus. The image input unit 130 includes, for example, acomposite terminal, S video terminal, D terminal, component terminal,analog RGB terminal, DVI-I terminal, DVI-D terminal, HDMI® terminal, andthe like. When the image input unit 130 receives an analog image signalor video signal, it converts the received analog signal into a digitalsignal, and transmits the digital signal to the image processing unit140. Note that the external apparatus is not particularly limited, andmay include a personal computer, camera, mobile phone, smartphone, harddisk recorder, game machine, and the like as long as they can output animage signal or video signal.

The image processing unit 140 includes, for example, an image processingmicroprocessor, applies change processing of the number of frames, thenumber of pixels, an image shape, and the like to an image signal orvideo signal received from the image input unit 130, and transmits theprocessed signal to the liquid-crystal control unit 150. The imageprocessing unit 140 need not always include a dedicated microprocessor.For example, the CPU 110 may execute the same processing as the imageprocessing unit 140 using a program stored in the ROM 111. The imageprocessing unit 140 can execute functions such as frame decimationprocessing, frame interpolation processing, resolution conversionprocessing, and distortion correction processing (keystone correctionprocessing). Also, the image processing unit 140 can also apply theaforementioned change processing to an image or video reproduced by theCPU 110 in addition to the signal received from the image input unit130. The detailed behavior related to the distortion correctionprocessing by this image processing unit 140 will be described later.

The liquid-crystal control unit 150 includes, for example, a controlmicroprocessor, and controls voltages to be applied to liquid crystalsof pixels of the liquid-crystal elements 151R, 151G, and 151B ofliquid-crystal panels based on an image signal or video signal processedby the image processing unit 140, thereby adjusting the transmittancesof the liquid-crystal elements 151R, 151G, and 151B. Note that theliquid-crystal control unit 150 need not always be a dedicatedmicroprocessor. For example, the CPU 110 may execute the same processingas the liquid-crystal control unit 150 using a program stored in the ROM111. For example, when a video signal is input to the image processingunit 140, the liquid-crystal control unit 150 controls theliquid-crystal elements 151R, 151G, and 151B to have transmittancescorresponding to an image every time it receives an image for one framefrom the image processing unit 140. The liquid-crystal element 151Rcorresponds to red, and adjusts a transmittance of red light of lightrays which are output from the light source 161 and are separated intored (R), green (G), and blue (B) light rays by the color separating unit162. The liquid-crystal element 151G corresponds to green, and adjusts atransmittance of green light of light rays which are output from thelight source 161 and are separated into red (R), green (G), and blue (B)light rays by the color separating unit 162. The liquid-crystal element151B corresponds to blue, and adjusts a transmittance of blue light oflight rays which are output from the light source 161 and are separatedinto red (R), green (G), and blue (B) light rays by the color separatingunit 162.

The light source control unit 160 includes, for example, a controlmicroprocessor, which executes ON/OFF control and light amount controlof the light source 161. Note that the light source control unit 160need not always be a dedicated microprocessor. For example, the CPU 110may execute the same processing as the light source control unit 160using a program stored in the ROM 111. The light source 161 includes,for example, a halogen lamp, xenon lamp, or high-pressure mercury lamp,and outputs light required to project an image onto a screen 180. Thecolor separating unit 162 includes, for example, a dichroic mirror andprism, and separates light output from the light source 161 into red(R), green (G), and blue (B) light components. Note that when LEDs orthe like corresponding to respective colors are used as the light source161, the color separating unit 162 is not necessary. The color composingunit 163 includes, for example, a dichroic mirror and prism, andcomposes red (R), green (G), and blue (B) light rays transmitted throughthe liquid-crystal elements 151R, 151G, and 151B. Then, light, the red(R), green (G), and blue (B) light components of which are composed bythe color composing unit 163, is sent to the projection optical system171. At this time, the liquid-crystal elements 151R, 151G, and 151B arecontrolled by the liquid-crystal control unit 150 so as to havetransmittances corresponding to an image input from the image processingunit 140. For this reason, when the light composed by the colorcomposing unit 163 is projected onto the screen via the projectionoptical system 171, an image corresponding to that input by the imageprocessing unit 140 is displayed on the screen.

The optical system control unit 170 includes, for example, a controlmicroprocessor, and controls the projection optical system 171. Notethat the optical system control unit 170 need not always be a dedicatedmicroprocessor. For example, the CPU 110 may execute the same processingas the optical system control unit 170 using a program stored in the ROM111. Also, the projection optical system 171 projects composed lightoutput from the color composing unit 163 onto the screen. The projectionoptical system 171 includes a plurality of lenses and an actuator fordriving the lenses, and can attain an enlargement/reduction, shift,focus adjustment, and the like of a projected image by driving thelenses by the actuator.

The recording/reproduction unit 191 reproduces still image data ormoving image data from the recording medium 192. Also, therecording/reproduction unit 191 receives still image data or movingimage data obtained by the imaging unit 194 from the CPU 110, andrecords the received data in the recording medium 192. Also, therecording/reproduction unit 191 may record still image data or movingimage data received from the communication unit 193 to the recordingmedium 192. The recording/reproduction unit 191 includes, for example,an interface required to electrically connect the recording medium 192,and a microprocessor required to communicate with the recording medium192. Note that the recording/reproduction unit 191 need not alwaysinclude a dedicated microprocessor. For example, the CPU 110 may executethe same processing as the recording/reproduction unit 191 using aprogram stored in the ROM 111. The recording medium 192 can record stillimage data, moving image data, control data required for the projectorof this embodiment, and the like. The recording medium 192 can includerecording media of every systems such as a magnetic disk, optical disk,and semiconductor memory, and may be either a detachable recordingmedium or built-in type recording medium.

The communication unit 193 is used to receive a control signal, stillimage data, moving image data, and the like from an external apparatus,and may include, for example, a wireless LAN, wired LAN, USB,Bluetooth®, or the like, since it is not particularly limited to aspecific communication system. On the other hand, when the terminal ofthe image input unit 130 is, for example, an HDMI® terminal, thecommunication unit 193 may make CEC communications via that terminal.Note that the external apparatus is not particularly limited, and mayinclude a personal computer, camera, mobile phone, smartphone, hard diskrecorder, game machine, remote controller, and the like, as long as theycan communicate with the projector 100.

The display control unit 195 includes a display control microprocessorand the like, and controls to display an operation screen and imagessuch as switch icons, which are required to operate the projector 100 onthe display unit 196 included in the projector 100. Note that thedisplay control unit 195 need not always be a dedicated microprocessor.For example, the CPU 110 may execute the same processing as the displaycontrol unit 195 using a program stored in the ROM 111. The display unit196 displays the operation screen and switch icons required to operatethe projector 100. The display unit 196 is not particularly limited aslong as it can display an image. For example, a liquid-crystal display,CRT display, organic EL display, or LED display may be used.Alternatively, the display unit 196 may control LEDs corresponding torespective buttons to emit light so as to allow the user to recognize aspecific button.

Note that the image processing unit 140, liquid-crystal control unit150, light source control unit 160, optical system control unit 170,recording/reproduction unit 191, and display control unit 195 may be oneor a plurality of microprocessors, which can execute the same processingas these operation blocks. Alternatively, for example, the CPU 110 mayexecute the same processing as the respective blocks using programsstored in the ROM 111.

<Basic Operation>

The basic operation of the projector 100 of this embodiment will bedescribed below with reference to FIGS. 1 and 2.

FIG. 2 is a flowchart showing the basic operation of the projector 100of this embodiment. The operation shown in FIG. 2 is implemented whenthe CPU 110 expands a program stored in the ROM 111 onto a work area ofthe RAM 112, and controls the respective operation blocks. The operationshown in FIG. 2 is started when the user turns on a power switch of theprojector 100 by the operation member 113 or remote controller. When theuser turns on the power switch of the projector 100 by the operationmember 113 or remote controller, the CPU 110 begins to supply electricpower from a power supply unit (not shown) to the respective units via apower supply control unit (not shown).

Next, the CPU 110 determines a display mode selected by the user byoperating the operation member 113 or remote controller (step S210). Oneof display modes of the projector 100 of this embodiment is an “inputimage display mode” for displaying an image or video input from theimage input unit 130. One of display modes of the projector 100 of thisembodiment is a “file reproduction/display mode” for displaying stillimage data or moving image data read out from the recording medium 192by the recording/reproduction unit 191. One of display modes of theprojector 100 of this embodiment is a “file reception/display mode” fordisplaying still image data or moving image data received from thecommunication unit 193. Note that this embodiment will explain a case inwhich the user selects the display mode. However, the display mode atthe power-ON timing may be either that at the previous end timing or oneof the display modes selected as a default display mode. In this case,the process of step S210 may be omitted.

The following description will be given under the assumption that theuser selects the “input image display mode” in step S210.

If the “input image display mode” is selected, the CPU 110 waits untilan image or video is input from the image input unit 130 (step S220). Ifthe image or video is input (YES in step S220), the process advances toprojection processing (step S230).

In step S230, the CPU 110 transmits the image or video input from theimage input unit 130 to the image processing unit 140, and instructs theimage processing unit 140 to deform the number of pixels, frame rate,and shape of the image or video and then to transmit the processed imagefor one frame to the liquid-crystal control unit 150. Then, the CPU 110instructs the liquid-crystal control unit 150 to control thetransmittances of the liquid-crystal elements 151R, 151G, and 151B ofthe liquid-crystal panels to match those according to tone levels of red(R), green (G), and blue (B) color components of the received image forone frame. Then, the CPU 110 instructs the light source control unit 160to control light to be output from the light source 161. The colorseparating unit 162 separates the light output from the light source 161into red (R), green (G), and blue (B) light components, and supplies therespective light components to the liquid-crystal elements 151R, 151G,and 151B of the liquid-crystal panels. Transmission light amounts of thelight components of the respective colors supplied to the liquid-crystalelements 151R, 151G, and 151B are limited for respective pixels of theliquid-crystal elements. The red (R), green (G), and blue (B) lightcomponents transmitted through the liquid-crystal elements 151R, 151G,and 151B are supplied to the color composing unit 163 and are composedagain. Then, the light composed by the color composing unit 163 isprojected onto the screen 180 via the projection optical system 171.

This projection processing is sequentially executed for each image ofone frame during projection of the image.

Note that when the user inputs an operation instruction of theprojection optical system 171 from the operation member 113 at thattime, the CPU 110 instructs the optical system control unit 170 tocontrol the actuator of the projection optical system 171 so as tochange a focal point of the projected image and to change an enlargementratio of the optical system.

The CPU 110 determines whether or not the user inputs a display modeswitching instruction from the operation member 113 during execution ofthis display processing (step S240). If the user inputs the display modeswitching instruction from the operation member 113 (YES in step S240),the CPU 110 returns to step S210, and determines the display mode again.At this time, the CPU 110 transmits a menu screen which prompts the userto select the display mode as an OSD (On Screen Display) image to theimage processing unit 140, and controls the image processing unit 140 tosuperimpose this OSD screen on the projected image. The user selects thedisplay mode while observing the projected OSD screen.

On the other hand, if the user does not input any display mode switchinginstruction from the operation member 113 during execution of thedisplay processing (NO in step S240), the CPU 110 determines whether ornot the user inputs a projection end instruction from the operationmember 113 (step S250). If the user inputs the projection endinstruction from the operation member 113 (YES in step S250), the CPU110 stops power supply to the respective operation blocks of theprojector 100, thus ending the projection processing. On the other hand,if the user does not input any projection end instruction from theoperation member 113 (NO in step S250), the CPU 110 returns to stepS220. After that, the CPU 110 repeats the processes of steps S220 toS250 until the user inputs the projection end instruction from theoperation member 113.

As described above, the projector 100 of this embodiment projects animage onto the screen.

Note that in the “file reproduction/display mode”, the CPU 110 reads outa file list or thumbnail data of respective files of still image dataand moving image data from the recording medium 192 from therecording/reproduction unit 191, and temporarily stores them in the RAM112. Then, the CPU 110 generates text images based on the file list orimages based on the thumbnail data of respective files, which aretemporarily stored in the RAM 112 using a program stored in the ROM 111,and transmits the generated images to the image processing unit 140.After that, the CPU 110 controls the image processing unit 140,liquid-crystal control unit 150, and light source control unit 160 inthe same manner as in the normal projection processing (step S230).

Next, the user inputs, via the operation member 113, a text or imageselection instruction corresponding to each of still image data ormoving image data recorded in the recording medium 192 on the projectedscreen. Then, the CPU 110 controls the recording/reproduction unit 191to read out the selected still image data or moving image data from therecording medium 192. The CPU 110 temporarily stores the readout stillimage data or moving image data in the RAM 112, and reproduces the stillimage data or moving image data based on a program stored in the ROM111.

Then, the CPU 110 sequentially transmits, for example, the reproducedmoving image data to the image processing unit, and controls the imageprocessing unit 140, liquid-crystal control unit 150, and light sourcecontrol unit 160 in the same manner as in the normal projectionprocessing (step S230). On the other hand, when the still image data isreproduced, the CPU 110 transmits the reproduced image to the imageprocessing unit 140, and controls the image processing unit 140,liquid-crystal control unit 150, and light source control unit 160 inthe same manner as in the normal projection processing (step S230).

In the “file reception/display mode”, the CPU 110 temporarily storesstill image data or moving image data received by the communication unit193 in the RAM 112, and reproduces the still image data or moving imagedata based on a program stored in the ROM 111. Then, the CPU 110sequentially transmits, for example, the reproduced moving image data tothe image processing unit 140, and controls the image processing unit140, liquid-crystal control unit 150, and light source control unit 160in the same manner as in the normal projection processing (step S230).On the other hand, when the still image data is reproduced, the CPU 110transmits the reproduced image to the image processing unit 140, andcontrols the image processing unit 140, liquid-crystal control unit 150,and light source control unit 160 in the same manner as in the normalprojection processing (step S230).

<Configuration of Image Processing Unit>

The configuration of the image processing unit of this embodiment willbe described below with reference to FIG. 3.

Referring to FIG. 3, the image processing unit 140 includes a signalprocessing unit 310, OSD superimposing unit 320, and deformationprocessing unit 330.

A source image signal s301 is input from the image input unit 130,recording/reproduction unit 191, or communication unit 193 according tothe display mode, as described above. On the other hand, a timing signals302 includes a vertical sync signal, horizontal sync signal, clocks,and the like synchronized with the source image signal s301, and issupplied from a supply source of the source image signal s301. Therespective blocks in the image processing unit 140 operate based on thetiming signal s302. However, a timing signal may be re-generated andused inside the image processing unit 140.

The signal processing unit 310 acquires a histogram and statisticalinformation such as APL of an image signal from the source image signals301, and applies signal processing such as IP conversion, frame rateconversion, resolution conversion, γ conversion, color gamut conversion,color correction, and edge emphasis in cooperation with the CPU 110. Aprocessed image signal s303 processed by the signal processing unit 310is output to the OSD superimposing unit 320.

In accordance with an instruction from the CPU 110, the OSDsuperimposing unit 320 superimposes user menu or operation guideinformation on the processed image signal s303 as an OSD image, andoutputs a generated OSD-superimposed signal s304 to the deformationprocessing unit 330.

The deformation processing unit 330 calculates coordinates of pixelsbefore and after deformation based on a predetermined deformationformula, applies deformation processing to the OSD-superimposed signals304, and outputs a deformed image signal s305.

Assume that the deformation processing unit 330 of this embodimentdeforms an image using projective conversion. This deformationprocessing will be described below with reference to FIG. 8.

Referring to FIG. 8, reference numeral 810 denotes an image beforedistortion correction (source image) having four points Ps1 to Ps4 asvertices; and 820, an image after distortion correction having fourpoints Pd1 to Pd4 as vertices.

Note that in the projective conversion, a relationship betweencoordinates (xs, ys) of the source image 810 and coordinates (xd, yd) ofthe deformed image 820 is expressed by:

$\begin{matrix}{\begin{bmatrix}{xs} \\{ys} \\1\end{bmatrix} = {{M\begin{bmatrix}{{xd} - {{xd}\; 1}} \\{{y\; d} - {y\; d\; 1}} \\1\end{bmatrix}} + \begin{bmatrix}{{xs}\; 1} \\{{ys}\; 1} \\0\end{bmatrix}}} & (1)\end{matrix}$

where M is a 3×3 projective conversion matrix from the deformed image tothe source image, and is input from the CPU 110 to the deformationprocessing unit 330. xs1 and ys1 are coordinates of one vertex Ps1 ofthe source image 810, and xd1 and yd1 are coordinate values of thevertex Pd1 of the deformed image 820.

If the coordinates (xs, ys) of the source image, which are calculated byequation (1), assume integers, a pixel value at the coordinates may beused as that at the coordinates (xd, yd) of the deformed image intact.However, the coordinates of the source image calculated by equation (1)do not always assume integers. In this case, by executing interpolationusing pixel values of surrounding pixels of the coordinates of thesource image, a pixel value at deformed coordinates (xd, yd) iscalculated. As the interpolation method, an arbitrary interpolationmethod such as bilinear, bicubic, and the like may be used. On the otherhand, when the coordinates of the source image calculated based onequation (1) fall outside the range of the source image 810, black or abackground color set by the user is set as a pixel value at thecoordinates.

The deformation processing unit 330 calculates pixel values for alldeformed coordinates in the aforementioned sequence, thereby generatinga deformed image.

Note that in the above example, the projective conversion matrix M isinput from the CPU 110 to the deformation processing unit 330.Alternatively, the projective conversion matrix M may be calculatedinside the image processing unit 140. Note that the projectiveconversion matrix M is uniquely calculated from points of four cornersof the source image and those of four corners of coordinates of thedeformed image. This method is known, and a description thereof will notbe given.

The deformed image signal s305 output from the deformation processingunit 330 is supplied to the liquid-crystal control unit 150, and isdisplayed on the liquid-crystal panels, as described above.

<Distortion Correction Processing & Zoom Operation>

The distortion correction processing by the projector 100 of thisembodiment will be described below with reference to FIGS. 4 to 6F.

FIGS. 5A and 5B show a projected region on the liquid-crystal panel, andthat projected onto a projection plane in contrast to each other. FIG.5A shows a projected image on the liquid-crystal panel, and FIG. 5Bshows that on the screen. FIG. 5A illustrates one representativeliquid-crystal panel.

When the entire surface of the liquid-crystal panel is projected as aprojected region 510 onto the screen, and when the projector 100 and thescreen do not relatively face to each other, the projected image on thescreen is a distorted rectangle 520, although the shape varies dependingon a tilt angle and optical conditions. Reference numerals P1 to P4denote points of four corners of the projected region on theliquid-crystal panel, that is, points to be moved as correction points.Reference numerals PS1 to PS4 denote points of four corners of theprojected image corresponding to the correction points P1 to P4.

FIG. 4 shows the distortion correction processing by the projector 100of this embodiment. The processing shown in FIG. 4 is implemented whenthe CPU 110 expands a program stored in the ROM 111 onto a work area ofthe RAM 112 and controls the respective operation blocks.

Referring to FIG. 4, the CPU 110 determines whether or not a startinstruction of processing for executing distortion correction by movingcorrection points of the four corners in an image (4-corner designateddistortion correction) is received from the user via the operationmember 113 or remote controller (step S401). If the CPU 110 determinesthat the 4-corner designated distortion correction start instruction isreceived from the user, the process advances to step S402.

Next, the CPU 110 determines whether or not a selection instruction of apoint to be moved of the correction points of the four corners isreceived from the user via the operation member 113 or remote controller(step S402). If the CPU 110 determines that the selection instruction ofthe point to be moved is received, the process advances to step S403. Atthis time, in order to present the correction point selected as thepoint to be moved in an easily understood manner, the CPU 110 maycontrol the OSD superimposing unit 320 to superimpose an OSD in thevicinity of that correction point. The display contents are notparticularly limited as long as that information allows the user tospecify the selected correction point. For example, a color in thevicinity of PS1 may be changed to an eye-catching color or that pointmay be flickered.

On the other hand, if the CPU 110 determines in step S402 that theinstruction is not received, the process jumps to step S411.

In step S403, the CPU 110 waits for a user's correction point moveinstruction. The correction point move instruction is a signal generatedwhen the user presses, for example, a direction key (up, down, left, orright) of the operation member 113 or remote controller. If the CPU 110determines that the correction point move instruction is received, theprocess advances to step S404. On the other hand, if the CPU 110determines that the instruction is not received, the process jumps tostep S411.

If the CPU 110 determines that the user has pressed the direction key,it calculates coordinates of the moved correction point on theliquid-crystal panel according to the pressed direction key (step S404).For example, when coordinates of the selected correction point P4 beforemovement are (x4, y4), and when the user has pressed the right key,coordinates after movement are (x4+m, y4) where m is a predeterminedmove amount.

Next, the CPU 110 determines whether or not the coordinates of the movedcorrection point calculated in step S404 fall within a projected regionof the liquid-crystal panel (step S405). Letting (xp, yp) be resolutionsof the liquid-crystal panel, if x4+m<0 or xp≦x4+m, it is determined thatthe coordinates fall outside the projected region of the liquid-crystalpanel (outside a projected range); if 0≦x4+m<xp, it is determined thatthe coordinates fall within the projected region of the liquid-crystalpanel (inside the projected range).

If the CPU 110 determines in step S405 that the coordinates of the movedcorrection point fall within the projected region of the liquid-crystalpanel, the process advances to step S408. On the other hand, if the CPU110 determines that the coordinates fall outside the projected region ofthe liquid-crystal panel, the process advances to step S406.

In step S406, the CPU 110 instructs the optical system control unit 170to drive the zoom lens to optically enlarge the projected image. Theoptical system control unit 170 drives the zoom lens according to theinstruction of the CPU 110 (step S406).

At this time, before the optical system control unit 170 drives the zoomlens, the CPU 110 may instruct the OSD superimposing unit 320 tosuperimpose an OSD message representing that enlargement processing ofthe projected image is to be executed. Alternatively, after the CPU 110receives a signal representing a zoom operation OK message from the uservia the operation member 113 or remote controller, it may instruct theoptical system control unit 170 to drive the zoom lens.

Alternatively, the CPU 110 may not issue a zoom lens driving instructionif it receives a move instruction once, but it may issue a zoom lensdriving instruction when it receives a continuous move instructionduring a predetermined period (for example, when the user keeps pressinga key of the operation member 113 or remote controller).

Next, the CPU 110 executes correction processing for moving coordinatesof the respective correction points of the four corners to the inside ofthe projected image (step S407). For example, letting (xc, yc) becoordinates of a zoom central point on the liquid crystal panel underoptical conditions at a certain timing, X and Y coordinates of a certaincorrection point after correction are set as follows with respect tocoordinates (xn, yn) of that correction point on the liquid crystalpanel.

X coordinate:

xn+xm (when xn<xc)

xn−xm (when xn≧xc)

Y coordinate:

yn+ym (when yn<yc)

yn−ym (when yn≧yc)

where (xm, ym) are predetermined correction amounts, which may bedetermined for each correction point according to a distance from avertex before correction or may be changed in proportion to a drivingamount of the zoom lens. This correction processing may be applied toall the four correction points, but may be applied to three correctionpoints except for the currently selected correction point or thatdesignated first. Alternatively, the correction processing may beapplied to only a correction point, coordinates of which have alreadybeen determined in step S409 (to be described later).

Also, in order to present the correction point, the coordinates of whichare corrected, to the user in an easily understood manner, the CPU 110may instruct the OSD superimposing unit 320 to superimpose an OSD in thevicinity of the correction point. The display contents are notparticularly limited as long as that information allows the user tospecify the correction point, the coordinates of which are corrected.For example, a color in the vicinity of the correction point, thecoordinates of which are corrected, may be changed to an eye-catchingcolor or that point may be flickered.

In step S408, the CPU 110 determines the coordinates of the selectedcorrection point P4 on the liquid-crystal panel to be the coordinatesafter movement calculated in step S403, and the process advances to stepS409. At this time, the CPU 110 instructs the OSD superimposing unit 320to superimpose lines coupling the correction points P1 to P4 on theprojected image. In this manner, the user can easily recognize the shapeafter correction.

The CPU 110 determines in step S409 whether or not a move endinstruction of the selected correction point is received from the uservia the operation member 113 or remote controller (step S409). Thisdetermination process can be attained by checking if a predetermined keysuch as an enter key or cancel key of the operation member 113 or remotecontroller is pressed. If the CPU 110 determines that the move endinstruction of the selected correction point is received, the processadvances to step S410. On the other hand, if the CPU 110 determines thatthe instruction is not received, the process returns to step S403.

In step S410, the CPU 110 instructs the deformation processing unit 330to deform an input image according to the coordinates of the correctionpoints at the time of step S409 (step S410). At this time, the CPU 110calculates a projective conversion matrix M required to projectcoordinates of the deformed image on the liquid-crystal panel onto thoseof the source image on the liquid-crystal panel, and transmits thatmatrix to the deformation processing unit 330. The deformationprocessing unit 330 deforms the input image according to the informationreceived from the CPU 110.

The CPU 110 determines in step S411 whether or not a 4-corner designateddistortion correction end instruction is received from the user via theoperation member 113 or remote controller (step S411). If the CPU 110determines that the distortion correction end instruction is received,this processing ends. On the other hand, if the CPU 110 determines thatthe instruction is not received, the process returns to step S402.

<Change State of Projected Image During Distortion CorrectionProcessing>

Change states of the projected image during the distortion correctionprocessing will be described below with reference to FIGS. 6A to 6F byassociating user operations with changes of the projected image on theprojection plane.

A case will be exemplified below wherein a projected image 520 does notinclude an entire target shape 530, as shown in FIG. 6A, before thebeginning of distortion correction processing.

Assume that the user selects the correction point P4 in step S402. Then,assume that the user presses the left key of the remote controller instep S403. At this time, the CPU 110 determines in steps S404 and S405that coordinates after movement of the correction point P4 fall outsidethe projected region of the liquid-crystal panel. For this reason, theprojected image 520 is enlarged by the optical system control unit 170in step S406.

The user presses the left key a predetermined number of times to set theprojected image 520 in a state in which it includes the target shape530, as shown in FIG. 6B. At this time, the processes of steps S403 toS409 are repeated inside the projector 100.

Next, assume that the user presses the up key of the remote controller.At this time, the CPU 110 determines in steps S404 and S405 that thecoordinates after movement of the correction point P4 fall within theprojected region of the liquid-crystal panel. Thus, the CPU 110 updatesthe coordinates of the correction point P4 in step S408.

When a point P4 on the screen of the correction point P4 matches thevertex of the target shape, the user presses the enter key of the remotecontroller to input a move end instruction.

After that, the process advances to step S410, and the projected imageis deformed, as shown in FIG. 6C.

Next, the user selects the correction points P3, P2, and P1 in turn bythe same sequence, and inputs move instructions so that the correctionpoints match the vertices of the target shape. Changes of the projectedimage in this case are, as shown in FIGS. 6D to 6F.

With the aforementioned sequence, the distortion correction can beexecuted so that the projected image matches the target shape. Asdescribed above, according to the projector of this embodiment, when theuser attempts to move the correction point to the outside of theprojected image at the distortion correction timing, the zoom lens isdriven to enlarge the projected image on the screen. With thisoperation, the projector of this embodiment can project adistortion-corrected image at an arbitrary position on the projectionplane irrespective of the projection state before the distortioncorrection.

Note that this embodiment has explained the sequence in which after thecoordinates of the correction point are determined in step S409, theprocess advances to step S410 to deform an image. However, every timethe coordinates of the correction point are updated in step S407 orS408, the image may be deformed.

Note that as another operation example of step S408, when steps S406 andS407 are executed once or more during movement of a certain correctionpoint (during a loop of steps S403 to S409), the respective blocks ofthe projector 100 may operate, as shown in FIG. 9.

The CPU 110 determines whether or not the pressed direction key is thatof a direction opposite to the direction key pressed upon execution ofthe enlargement processing using the zoom lens in step S406 (step S901).If the CPU 110 determines the opposite direction, the process advancesto step S902. On the other hand, if the CPU 110 determines the samedirection, the process advances to step S904.

In step S902, the CPU 110 instructs the optical system control unit 170to drive the zoom lens to reduce the projected image. The optical systemcontrol unit 170 drives the zoom lens according to the instruction ofthe CPU 110 (step S902).

Next, the CPU 110 executes correction processing of the coordinates ofthe correction points of the four corners (step S903). Letting (xc, yc)be coordinates of a zoom central point, X and Y coordinates of a certaincorrection point after correction are respectively set as follows withrespect to coordinates (xn, yn) before correction.

X coordinate:

xn+xm (when xn<xc)

xn−xm (when xn≧xc)

Y coordinate:

yn+ym (when yn<yc)

yn−ym (when yn≧yc)

where (xm, ym) are predetermined correction amounts, which are desirablyamounts used in step S407 executed when the direction key opposite tothe currently pressed direction key is pressed.

In step S904, the CPU 110 determines the coordinates of the selectedcorrection point P4 on the liquid-crystal panel to be those aftermovement, which are calculated in step S403.

The other operation example of step S408 has been described. Forexample, when the user makes a wrong key operation to unnecessarilyenlarge the projected image, a zoom state can be reverted. For thisreason, compared to a case in which the zoom state is not reverted,unnecessary resolution deterioration caused by distortion correction canbe suppressed.

On the other hand, if the CPU 110 determines in step S406 that the zoomstate reaches a wide-angle end, and enlarged projection cannot beexecuted any more, it may instruct the OSD superimposing unit 320 tosuperimpose a warning OSD, and the process may return to step S403.Alternatively, the CPU 110 may instruct the optical system control unit170 to drive a shift lens in accordance with the received direction ofthe direction key so as to shift the projected image.

Second Embodiment

A projector of this embodiment is configured to also interlock a shiftlens. Note that the overall configuration and basic operation of theprojector, and the configuration of an image processing unit are thesame as those of the first embodiment, and a description thereof willnot be repeated.

FIG. 7 shows the operation of a projector 100 of this embodiment. Theoperation shown in FIG. 7 is implemented when a CPU 110 expands aprogram stored in a ROM 111 onto a work area of a RAM 112 and controlsrespective operation blocks. Since processes of steps S701 to S705 inFIG. 7 are the same as those of steps S401 to S405 in FIG. 4, adescription thereof will not be repeated.

Referring to FIG. 7, if the CPU 110 determines in step S705 thatcoordinates after movement of a correction point fall outside aprojected region, the process advances to step S706.

The CPU 110 determines in step S706 whether it instructs an opticalsystem control unit 170 to drive a zoom lens to attain a zoom operationor to drive a shift lens to attain a lens shift operation.

In this determination process, for example, when any or all ofcoordinates of remaining three correction points have already beendetermined, the zoom operation is to be executed; otherwise, the lensshift operation is to be executed. The determination method is notlimited to this. For example, when the zoom lens cannot be driven to anenlargement side any more, it may be determined that the lens shiftoperation is to be executed. If the CPU 110 determines that the zoomoperation is to be executed, the process advances to step S707;otherwise, the process advances to step S708.

In step S707, the CPU 110 instructs the optical system control unit 170to drive the zoom lens so as to optically enlarge the projected image.The optical system control unit 170 drives the zoom lens according tothe instruction of the CPU 110 (step S707).

In step S708, the CPU 110 instructs the optical system control unit 170to drive the shift lens so as to move the projected image on the screen.The optical system control unit 170 drives the shift lens according tothe instruction of the CPU 110 (step S708). The shift direction in thiscase matches the moving direction of the correction point determined instep S703.

In step S709, the CPU 110 executes correction processing of coordinatesof correction points of four corners (step S709). For example, usingpredetermined correction amounts (xk, yk), corrected coordinates arecalculated as (xn−xk, yn−yk) with respect to coordinates (xn, yn) of acertain correction point before correction.

This correction processing may be executed for three correction pointsexcept for the currently selected correction point or for onlycorrection points, coordinates of which have already been determined.Note that the correction amounts may assume different values forrespective correction points, or may be changed according to the drivingamount of the zoom lens or shift lens.

In order to present the correction point, coordinates of which arecorrected, to the user in an easily understood manner, the CPU 110 mayinstruct an OSD superimposing unit 320 to superimpose an OSD in thevicinity of the correction point. The display contents are notparticularly limited as long as the information allows the user tospecify the correction point, coordinates of which are corrected. Forexample, a color in the vicinity of the correction point, coordinates ofwhich are corrected, may be changed to an eye-catching color or thatpoint may be flickered.

Processes of subsequent steps S710 to S713 are the same as those ofsteps S408 to S411 in FIG. 4, and a description thereof will not berepeated.

<Change State of Projected Image During Distortion CorrectionProcessing>

Change states of the projected image during the distortion correctionprocessing will be described below with reference to FIGS. 10A to 10G byassociating user operations with changes of the projected image on aprojection plane. A case will be exemplified below wherein a projectedimage 520 does not include an entire target shape 530, as shown in FIG.10A, before the beginning of distortion correction processing.

Assume that the user selects the correction point P2 in step S702. Then,assume that the user presses the left key of the remote controller instep S703. At this time, the CPU 110 determines in steps S704 and S705that coordinates after movement of the correction point P2 fall outsidea projected region of a liquid-crystal panel. In this case, sincecoordinates of correction points P1, P3, and P4 other than the point P2are not changed yet, the CPU 110 determines that the lens shiftoperation is to be executed.

The user presses a right key a predetermined number of times to move theprojected image 520 to the right, as shown in FIG. 10B. At this time,the processes of steps S703 to S711 are repeated inside the projector100. The user presses an enter button of a remote controller, thusending movement of the projected image.

Since subsequent FIGS. 10C to 10G are the same as FIGS. 6B to 6F, adescription thereof will not be repeated.

With the aforementioned sequence, distortion correction can be executed,so that the projected image matches the target shape.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (for example, non-transitorycomputer-readable storage medium) to perform the functions of one ormore of the above-described embodiment(s) of the present invention, andby a method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiment(s). The computer may comprise one or more ofa central processing unit (CPU), micro processing unit (MPU), or othercircuitry, and may include a network of separate computers or separatecomputer processors. The computer executable instructions may beprovided to the computer, for example, from a network or the storagemedium. The storage medium may include, for example, one or more of ahard disk, a random-access memory (RAM), a read only memory (ROM), astorage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2012-179886, filed Aug. 14, 2012 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image projection apparatus comprising: aprojection unit configured to project an image onto a projection plane;a correction unit configured to correct a range of the image projectedby said projection unit; a deformation unit configured to deform theprojected range of the image according to a designated correction point;and a control unit configured to optically change the projected range ofthe image projected by said projection unit according to a designationof an outside of a predetermined range as the correction point.
 2. Theapparatus according to claim 1, wherein said control unit enlarges theprojected range of the image projected by said projecting unit accordingto the designation of the outside of the predetermined range as thecorrection point.
 3. The apparatus according to claim 2, wherein saidcontrol unit enlarges the projected range of the image projected by saidprojecting unit by driving a zoom lens included in said projection unitin an enlarging direction according to the designation of the outside ofthe predetermined range as the correction point.
 4. The apparatusaccording to claim 1, wherein said control unit moves the projectedrange of the image projected by said projecting unit according to thedesignation of the outside of the predetermined range as the correctionpoint.
 5. The apparatus according to claim 4, wherein said control unitmoves the projected range of the image projected by said projecting unitby moving a position of a lens included in said projection unit in aplane perpendicular to an optical axis of the lens according to thedesignation of the outside of the predetermined range as the correctionpoint.
 6. The apparatus according to claim 1, wherein said control unitenlarges the projected range of the image projected by said projectingunit according to the designation of the outside of the predeterminedrange as the correction point, and said control unit further moves acorrection point different from the correction point, which isdesignated to be moved to the outside of the predetermined range, to aninside of the projected range.
 7. The apparatus according to claim 1,wherein said control unit executes enlargement of the projected range ofthe image projected by said projection unit in priority to movement ofthe projected range of the image projected by said projection unit. 8.The apparatus according to claim 1, wherein said control unit inhibitsdesignation of the outside of the projected range for a correction pointwhich is not the correction point which is designated first of thecorrection points.
 9. The apparatus according to claim 1, wherein saidprojection unit displays an image representing the correction point onthe projection plane.
 10. A control method of an image projectionapparatus having a projection unit configured to project an image onto aprojection plane, a correction unit configured to: correct a range ofthe image projected by the projection unit, and a deformation unitconfigured to deform the projected range of the image according to adesignated correction point, the method comprising optically changingthe projected range of the image projected by the projection unitaccording to a designation of an outside of a predetermined range as thecorrection point.
 11. The method according to claim 10, wherein theprojected range of the image projected by the projecting unit isenlarged according to the designation of the outside of thepredetermined range as the correction point.
 12. The method according toclaim 11, wherein the projected range of the image projected by theprojecting unit is enlarged by driving a zoom lens included in theprojection unit in an enlarging direction according to the designationof the outside of the predetermined range as the correction point. 13.The method according to claim 10, wherein the projected range of theimage projected by the projecting unit is moved according to thedesignation of the outside of the predetermined range as the correctionpoint.
 14. The method according to claim 13, wherein the projected rangeof the image projected by the projecting unit is moved by moving aposition of a lens included in the projection unit in a planeperpendicular to an optical axis of the lens according to thedesignation of the outside of the predetermined range as the correctionpoint.
 15. The method according to claim 10, wherein the projected rangeof the image projected by the projecting unit is enlarged according tothe designation of the outside of the predetermined range as thecorrection point, and a correction point different from the correctionpoint, which is designated to be moved to the outside of thepredetermined range, is moved to an inside of the projected range. 16.The method according to claim 10, wherein enlargement of the projectedrange of the image projected by the projection unit is executed inpriority to movement of the projected range of the image projected bythe projection unit.
 17. The method according to claim 10, wherein theoutside of the projected range is inhibited from being designated for acorrection point which is not the correction point which is designatedfirst of the correction points.
 18. The method according to claim 10,wherein an image representing the correction point is displayed on theprojection plane.